Question

When I created a nested hastable in wcf, I get an error which is “The underlying connection was closed: The connection was closed unexpectedly.”
I don’t know where is the problem.

Client code

    private static List<Playlist> remotePlaylistArray;
    private static List<Playlist> _PlaylistArray;
    public static List<Playlist> PlaylistArray
    {
        get
        {
            if (_PlaylistArray == null)
            {
                _PlaylistArray = myClient.GetPlaylists(Username, Password, (int)UserInf["id"], "%").Select(i => new Playlist
                (
                    i["name"].ToString(),
                    true,
                    ((Hashtable[])i["medias"]) == null ? null :
                    ((Hashtable[])i["medias"]).Select(ix => new YoutubeMedia()
                    {
                        Duration = ix["duration"].ToString(),
                        Title = (string)ix["title"],
                        ID = (string)ix["videoinf"]
                    }).ToArray()
                ) { ID = (int)i["id"] }).ToList();//The underlying connection was closed: The connection was closed unexpectedly.

                remotePlaylistArray = new List<Playlist>(_PlaylistArray);
            }

            return _PlaylistArray;
        }

Service Code

    public IEnumerable<Hashtable> GetPlaylistItems(string username, string password, int pid)
    {
        return this.ExecuteHashtable("GetPlaylistItems", username, Crypter.DoTwiceMD5(password), pid);
    }

    public IEnumerable<Hashtable> GetPlaylists(string username, string password, int userid, string filter)
    {
        List<Hashtable> list = this.ExecuteHashtable("GetPlaylists", username, Crypter.DoTwiceMD5(password), userid, filter).ToList();

        foreach (var item in list)
        {
            Hashtable[] arr = GetPlaylistItems(username, password, (int)item["id"]).ToArray();
            item.Add("medias", arr.Length != 0 ? arr : null);
        }

        return list;
    }

the exception comes from tracelistener is

Type ‘System.Collections.Hashtable[]’ with data contract name ‘ArrayOfArrayOfKeyValueOfanyTypeanyType:http://schemas.microsoft.com/2003/10/Serialization/Arrays’ is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types – for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

Answer 1

What happens in your case is that HashTable is not directly serializable, so if it’s really necessary for you to return a HashTable you have to write a custom serializer.

One question: does your server side know the Playlist type? If yes, I would highly recommend you to return a List instead of a HashTable …